Accessing fields of a custom object type

Question

Hello,
this is for Oracle 11.2.0.4.0
I am trying to create and return an object inside a function and then access attributes of that object.
It works in that I get the expexted result in my query, but the object is created once again for each attribute that I am accessing:
CREATE OR REPLACE TYPE zzz_tp_type_test AS OBJECT (
  col_a VARCHAR2(100 CHAR),
  col_b VARCHAR2(100 CHAR),
  col_c VARCHAR2(100 CHAR)
CREATE OR REPLACE FUNCTION zzz_f_type_test RETURN zzz_tp_type_test
IS
  ret zzz_tp_type_test := zzz_tp_type_test('aa', 'bb', 'cc');
BEGIN
  dbms_output.put_line('Running once...');
  RETURN ret;
END;
SET serveroutput ON;
SELECT (A).col_a, (A).col_b, (A).col_c FROM (
    SELECT zzz_f_type_test A FROM dual
The result of the SELECT query is
(A).COL_A
(A).COL_B
(A).COL_C
aa
bb
cc
Running once...
Running once...
Running once...
I am not sure why this is happening, or how to prevent this. I would expect to call the function only once, and then access that one created instance for each attribute.
I am thinking it might have to do with the parentheses around "A", but that was the only way to get the query to execute - without them I got a syntax error.
What do I need to change for the DB to execute the function only once?
Thank you...

Answer 1

That's a good solution using a table type and table function.  It can be simplified a bit, as shown below.
SCOTT@orcl> -- test environment:
SCOTT@orcl> select banner from v$version
  2  /
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE    11.2.0.1.0    Production
TNS for 64-bit Windows: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
5 rows selected.
SCOTT@orcl> -- original type and function:
SCOTT@orcl> CREATE OR REPLACE TYPE zzz_tp_type_test AS OBJECT (
  2        col_a VARCHAR2(100 CHAR),
  3        col_b VARCHAR2(100 CHAR),
  4        col_c VARCHAR2(100 CHAR)
  5      );
  6  /
Type created.
SCOTT@orcl> CREATE OR REPLACE FUNCTION zzz_f_type_test
  2    RETURN zzz_tp_type_test
  3  IS
  4    ret zzz_tp_type_test := zzz_tp_type_test('aa', 'bb', 'cc');
  5  BEGIN
  6    dbms_output.put_line('Running once...');
  7    RETURN ret;
  8  END;
  9  /
Function created.
SCOTT@orcl> SET SERVEROUTPUT ON
SCOTT@orcl> -- additional type from Gerard:
SCOTT@orcl> create or replace type zzz_nt_type_test is table of zzz_tp_type_test;
  2  /
Type created.
SCOTT@orcl> -- simplification of Gerard's query:
SCOTT@orcl> select i.col_a, i.col_b, i.col_c
  2  from  table (zzz_nt_type_test (zzz_f_type_test())) i
  3  /
COL_A
COL_B
COL_C
aa
bb
cc
1 row selected.
Running once...
SCOTT@orcl> exec dbms_output.put_line('end');
end
PL/SQL procedure successfully completed.
SCOTT@orcl>